Family

Genera

Family ARACANIDAE

Common name: Keeled boxfishes, temperate boxfishes, trunkfishes

Summary:

A small family of oval to round fishes with bodies almost completely encased in a bony carapace formed from large thickened scale plates, usually hexagonal in shape and firmly sutured to one another; except the caudal peduncle which has isolated plates to allow tail movement. All species have very small mouths and often locate their invertebrate prey by blowing a jet of water onto the sediment. See Matsuura 2014.

Boxfishes lack fin spines and pelvic fins, and the short-based dorsal and anal fins are set far back on the body.

The rigid plates end before or on the tail base which is never completely enclosed in fused plates. The carapace has a series of longitudinal ridges, including a ventral ridge, and bear large fixed spines in some species.

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Family Taxonomy

A small family with 12 species in six genera, with 9 species found in Australia.

Family Distribution

Indo-West Pacific

Family Description

Body nearly completely enclosed in a carapace formed of enlarged, thickened scale plates, usually hexagonal in shape and firmly sutured to one another (less so on the cheek to allow for breathing movements); the carapace with openings for the mouth, eyes, gill slits, and fins, and for the flexible caudal peduncle.

Body oval in cross section; scales large, hexagonal, fused into a rigid bony carapace, covering body in front of dorsal and anal fins; centre of each individual plate with a low tubercle and radiating low ridges connecting adjoining plates; surface features indistinct in large individuals.

Species are sexually dimorphic, and males often become brightly coloured and develop a hump on the head or elongate spines in some species.

Family Feeding

Carnivores, usually feeding on invertebrates such as crustaceans. Temperate boxfishes have very small mouths and often blow a jet of water onto the sediment to expose their prey.

Family Reproduction

The sexes are separate and fertilization is external; eggs and larvae are pelagic.

Family Commercial

Although of no interest to fisheries, temperate boxfishes are often taken as bycatch in commercial trawls.

Family Conservation

No species are listed in Australia. Some species distributed elsewhere have been assessed as Least Concern by the IUCN.

Family Remarks

Although the flesh not poisonous, a mucous toxin, ostracitoxin, is present and some species can secrete the poison under stress. This toxin kills other fish and, eventually the boxfish themselves if exposed to it.

The precise location of this toxin in all species is not fully understood, and boxfish should be considered potentially toxic to humans and their consumption as food should be avoided.

Matsuura, K. 2014. Taxonomy and systematics of tetraodontiform fishes: a review focusing primarily on progress in the period 1980 to 2014. Review for IPFC9 Special Issue. Ichthyological Research 62(1): 72-113. Open access DOI:10.1007/s10228-014-0444-5